Low-Energy Spectrum of Cosmic Rays as an Indicator of Primary Source Characteristics and Interstellar Propagation

The low-energy spectra of protons and helium nuclei, recently measured by McDonald and Ludwig, and by Fan, Gloeckler, and Simpson are corrected for solar modulation according to Parker's model and for diffusive passage through interstellar matter. The resulting source spectrum is exhibited and compared with the spectrum of accelerated particles inferred from high-energy data and from an energy-equipartition argument due to Syrovatskii. This analysis yields a transmission function for the source environment which is similar in form to the velocity-dependent solar modulation of low-energy particles.